Ebola Vaccine Trials Prove Successful

ebola vaccine

A woman takes part in an Ebola virus vaccine trial in Monrovia, Liberia. (Photo credit: Abbas Dulleh/AP Images)

Last summer, the Ebola outbreak in West Africa was all over the news. At the outbreak’s height, many health officials feared the disease would spread across the globe, and indeed individuals in the United States and Europe were diagnosed with the disease. However, cases outside of West Africa were kept isolated and a global outbreak of the disease was prevented.

While Ebola is no longer making headlines, it is still an ongoing problem in West Africa. Since instances of a disease with Ebola-like symptoms were first reported in March 2013, as of July 2015, a total of 27,748 Ebola cases have been identified in Guinea, Liberia, and Sierra Leone. Of these cases, there have been 11,279 reported deaths, although it is believed that the actual number of deaths may be much higher.

Since the outbreak began, scientists have been in a race to develop a vaccine to stop the spread of the disease. Due to an unprecedented collaboration between researchers, doctors, financial donors, and pharmaceutical companies, the usual decades-long process to create and vet a vaccine has been reduced to a year, and researchers are already testing vaccines on human volunteers.

Trials of a single-dose vaccine called rVSV-ZEBOV (Merck, Sharpe & Dohme) began on March 23, 2015. The goal of the trial is to test the vaccines’ success rate, effectiveness, and safety. rVSV-ZEBOV uses a genetically engineered version of vesicular stomatitis virus – an animal virus that mainly infects cattle – to carry a gene segment of the Ebola virus. This gene segment cannot cause occurrences of Ebola on its own.

The trial uses a “ring design” vaccination strategy. “The ‘ring’ vaccination method adopted for the vaccine trial is based on the smallpox eradication strategy,” John-Arne Røttingen, Director of the Division of Infectious Disease Control at the Norwegian Institute of Public Health and Chair of the Study Steering Group said in a World Health Organization (WHO) news release. “The premise is that by vaccinating all people who have come into contact with an infected person you create a protective ‘ring’ and stop the virus from spreading further. This strategy has helped us to follow the dispersed epidemic in Guinea, and will provide a way to continue this as a public health intervention in trial mode.”

Some of the rings are vaccinated soon after a case of Ebola is detected, while others are vaccinated three weeks after detection. According to the WHO news release, this study design is an alternative to using a placebo. It instead uses a randomized control group for comparison, and thus still allows for all individuals who have been in contact with an Ebola patient to be vaccinated in the trial. As of late July, over 4000 individuals have been voluntarily vaccinated against Ebola. These individuals are family members, neighbors, and co-workers of nearly 100 Ebola patients. Trials conducted in Guinea have thus far had a 100% success rate.

“This is a remarkable result which shows the power of equitable international partnerships and flexibility,” Jeremy Farrar, Director of the Wellcome Trust, one of the funders of the trial, said in the WHO news release. “This partnership also shows that such critical work is possible in the midst of a terrible epidemic. It should change how the world responds to such emerging infectious disease threats. We, and all our partners, remain fully committed to giving the world a safe and effective vaccine.”

Given the vaccine’s success rate, as of July 26, randomization is no longer a priority, and all people at risk for contracting Ebola are immediately receiving the vaccine. In addition, the trial has also begun to include 13- to 17-year-olds and children aged 6-12 also soon may be able to receive the vaccine.

Ebola vaccine trials are not just occurring at ground zero in West Africa. Fargo, North Dakota is one of 40 cities around the world where the vaccine is also being tested. Volunteers that take part in the six-month vaccination study require four doctor visits: one for the vaccination shot, two for bloodwork, and one for a final check-up. The goal of the study is to “explore the vaccine’s ability to safely generate antibodies that could protect against future exposure to the virus.” Unlike the vaccine trials in West Africa, in this study, 90 percent of the volunteers will receive the vaccine while 10 percent will receive a placebo.

In addition to these vaccine trials, several other potential Ebola vaccines are also in various stages of the research and development process and are being tested in the United States, Canada, Kenya, and the United Kingdom.

More to Explore
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Ebola: Mapping the Outbreak
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WHO: Trials show new Ebola vaccine is ‘highly effective’
World on the Verge of an Effective Ebola Vaccine
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